Jim Swire, the British representative of the relatives, said last night: 'It is an important victory. It opens the way for substantial compensation claims, but more than that, it means airlines will at last take security seriously because it will cost too much not to.'
After three days of deliberation the jury in Brooklyn ruled in favour of the relatives of the 270 victims of Flight 103, who sued the airline claiming the baggage handling had suffered from lax security. An unaccompanied suitcase held the bomb that exploded over Lockerbie on 21 December 1988.
The result could open the way to multi-million dollar damages claims against the Pan Am insurer, United States Aviation Insurance Group (USAIG). The airline is no longer flying. Airlines throughout the world could be forced to review their security in light of the ruling.
Another trial will be needed to assess any damages claim, and none has yet been scheduled.
Dr Swire said that money alone could never compensate for the loss of a relative, but welcomed the implications the ruling would have for airline security.
He said technology able to identify unaccompanied baggage - similar to that containing the Lockerbie bomb - already existed. But it was not being widely installed at airports because of the costs involved. He said the threat of having to settle massive compensation claims in the wake of the decision in the New York case would give airline companies and their insurers a financial incentive to introduce new security systems.
'It sickens me that these changes are spurred for financial rather than humanitarian reasons, but that's just the way it is.'
Peter Watson, British lawyer for the families, said on the BBC that the decision would force airlines to tighten security.
'It's a warning to the airline industry that if their security is as lax, poor and haphazard as Pan Am's was on this occasion, then they face fearful damages. That is the only way a court can bring this home to an airline.'
Yesterday's verdict was greeted with sighs of relief by the many relatives and friends of the victims who crowded the courtroom. The suit sought up to dollars 500m ( pounds 277m) in damages from the airline, which would be paid by the USAIG.
Under international treaties the amount of damages is limited to dollars 75,000 ( pounds 40,000) for each victim, but the 'wilful misconduct' verdict means that much higher damages can now be paid.
The outcome of the trial in the US also strengthens the case against Libya. The insurance company tried to persuade the jury that the bomb was put on the aircraft in London or Frankfurt because of a slip-up in a drug operation mounted by American intelligence and that there was little the airline could have done to prevent the bombing.
Lawyers for the families argued that Pan Am was criminally negligent in its security procedures at Frankfurt and elsewhere around the world, making it possible for a bomb to be put on board the flight from a connecting airline. The defence team believes, as do the Scottish police, that the bomb was placed on a flight in Malta and checked through to New York via Frankfurt and London.
Two Libyan intelligence agents have been charged in Scottish and American courts with engineering the bombing and Libya's refusal to hand them over for trial has led to sanctions being imposed by the United Nations Security Council.